Tuesday, December 13, 2016

Just a Chinese Hoax?

Current climate change may be a major threat to global biodiversity, but the extent of species loss will depend on the details of how species respond to changing climates. For example, if most species can undergo rapid change in their climatic niches, then extinctions may be limited. Numerous studies have now documented shifts in the geographic ranges of species that were inferred to be related to climate change, especially shifts towards higher mean elevations and latitudes.

Climate change is predicted to threaten many species with extinction, but determining how species will respond in the future is difficult. A way to understand this better is to study the extinctions caused by the climate change which have already occurred. This also includes local extinctions as they document the loss of populations at the climate edge of species’ ranges e.g at lower elevations and latitudes. Many studies already demonstrated that species are shifting their geographic ranges over time as the climate warms, towards cooler habitats at higher elevations and latitudes. A new study used these range-shift studies to show that local extinctions have already happened in the warmest parts of the ranges of more than 450 plant and animal species. This result is particularly concerning because so far global warming has increased mean temperatures by less than 1 degree Celsius. These extinctions will almost certainly become much more widespread over time, because temperatures are predicted to increase by an additional 1 to 5 degrees in the next several decades no matter if ignorant politicians believe it or not. These local extinctions could also soon extend to species that humans depend on for food and resources.

The study also tested the frequency of local extinction across different regions, habitats, and groups of organisms. It found that local extinctions occurred in about half of the species surveyed across different habitats and taxonomic groups. However, the results showed that local extinctions varied by region and were almost twice as common among tropical species as among temperate species. This is important as the majority of plant and animal species live in the tropics.

A major conclusion of this study is that populations of many species are already unable to undergo niche shifts that are fast enough to prevent local extinction from climate change. The rate is emphasized here because even if the absolute amount of niche change needed to avoid extinction might be attainable, it might require more time to achieve than is allowed by the rapid pace of anthropogenic climate change.